The invention relates to a stator for an electronically commutated electric motor, as well as to a method according to the invention.
The subject matter of the invention concerns the production of armature windings for an electronically commutated electric motor, which makes feasible implementing a construction method for high efficiency at high economy.
In power-assisted steering systems for motor vehicles especially high demands are made in particular of the motor drives. Due to the required highly compact type of construction and high required driving powers, correspondingly high efficiencies are necessary in electric motors. In addition, in such mass-produced products, the production costs in the automobile industry must be appropriately low, which makes necessary high economy in the production of such a drive. Therefore for such drives electronically commutated electric motors are increasingly employed, such as are described for example in EP 1 499 003 A1. Here the multiphase stator windings disclosed are wound successively for each phase onto the stator poles and its wires are connected with one another outside of the stator after the winding of each phase disposition to form a three-phase system. Each of the three phases contains three stator poles with the associated windings, each of which forms a pole group per phase. Within each pole group the winding direction from one pole to the next is disposed alternatingly and provided for all three pole groups equidirectionally and identically. Within prior art this has been the conventional approach for a long time in order to place windings around three-phase pole groups and in order to implement thereby a rotationally symmetric winding disposition for the generation of a rotary field for an electric motor.
Placing windings on compact stators is highly complex and expensive and especially the connection of a multiplicity of wires outside of the stator leads to additional expenditures and to undesirable stray fields which makes the disposition less economical.
A disposition improved in this regard is described in WO 2007/012207. Here the stator poles are all successively wound with one wire without interruption. The apportionment into the pole groups of the phases takes place thereby that at the desired sites the wires are carried out at the end side on the stator via a type of loop and carried back again, such that here at this site the wire packet can be contacted and, where necessary, can be cut open and contacted such that in the end region of the stator the desired pole groups can be wired to form the designated multiphase winding configuration. The winding of all poles herein takes place using a single wire from one pole to the other, always with alternating sense of winding. While placing the winding is hereby simplified, the end-side wiring to form the multiphase winding configuration herein takes place over the entire circumferential region of the stator. Relatively many terminal point sites become thereby necessary and the stray fields generated here are also distributed over the circumference and it is difficult to dispose here with optimal effect in the end side region sensors for the motor control.